Free-volume chamber for telescoped caseless ammunition



Sept. 15,1970 v J. l. HARRELL 3,523,137

FREE-VOLUME CHAMBER FOR TELESCOPEIICASELESS AMMUNITIUN Filed Oct. 23,1968 20 l4 I8 34 36 22 I6 IO 24 26 2730 32 I2 FIG.2

48 66 3 JOSEPH LHARRELL INVENTUR.

ATTORNEY United States Patent 3 528 187 FREE-VOLUME CHAMBER FORTELESCOPED CASELESS AMMUNITION Joseph I. Harrell, Sparta, NJ., assignorto Hercules Incorporated, Wilmington, DeL, a corporation of DelawareFiled Oct. 23, 1968, Ser. No. 769,908

Int. Cl. F41c 21/00, 21/12; F41b 5/18 U.S. Cl. 42-76 6 Claims ABSTRACTOF THE DISCLOSURE A chamber designed for the firing of telescopedcaseless ammunition is provided. The chamber has one or more cavities inits interior surface which provide areas of support and non-support atspecific locations for the propellant charge of the telescoped round.Ballistic efliciency of telescoped rounds fired in this chamber issubstantially improved.

This invention relates to a free-volume chamber for receiving atelescoped round of casel ss ammunition, said chamber increasing theballistic efiiciency of the telescoped caseless round fired therein.More particularly this invention relates to a chamber having free volumewhich provides areas of support and non-support about the propellantcharge of a telescoped round of caseless ammunition loaded therein toincrease ballistic performance of the round.

Telescoped caseless ammunition is comprised of a propellant chargehaving an axial bore or cavity, a projectile housed entirely within theaxial bore of the propellant charge and a primer. Various embodiments oftelescoped caseless ammunition are disclosed in patent application S.N.694,310, now Pat. No. 3,482,516; filed Dec. 28, 1967 by L. I. Farmer etal. and entitled Caseless Cartridges Having the Projectile Housed in thePropellant Charge.

When a telescoped round of caseless ammunition is loaded into thechamber of a gun, the projectile being housed in the propellant chargeis not seated in the barrel of the gun as is the projectile of a roundof conventional ammunition when in a loaded position. Upon initiation ofthe primer of the telescoped round, the projectile is forced forwardinto the barrel of the gun and becomes seated in the barrel. During thetime interval from initiation of the primer until the projectile isseated in the barrel of the gun, some of the gases of combustion fromthe primer and from the initiated propellant charge can escape throughthe barrel of the gun ahead of the projectile resulting in a loss ofpropulsive gas. This loss in propulsive gas results in reduction in theballistic performance of the round.

It has now been discovered that by providing various areas of supportand non-support about the propellant charge in specific locations of thegun chamber that ballistic performance of telescoped caseless ammunitioncan be substantially improved. The areas of support and nonsupportprovided by the free-volume chamber and their locations in the chamberare defined hereinafter in relation to a round of telescoped caselessammunition loaded in the chamber. The round of telescoped caselessammunition loaded into the free-volume chamber must be sized so thatthere is a close fit betwen the propellant charge and the inside wallsof the chamber. Free-volume is provided by at least one aft cavity inthe inside peripheral surface of the chamber. The portion of thepropellant charge opposite the cavity is not supported, while theremaining portion of the propellant charge which by design is contiguouswith the inside walls of the chamber, is supported. The location of theaft cavity or aft cavities in the free-volume chamber depends upon theposition of the Patented Sept. 15, 1970 ice forward rim of the rotatingband of the projectile housed in the propellant charge. It is necessarythat the forwardmost edge of any aft cavity be located no fartherforward in the chamber body than the forward rim of the projectilerotating band.

For a complete understanding of this invention, reference is made to thefollowing detailed description and drawings.

FIG. 1 is an elevational view partly broken away and in section of afree-volume chamber with a round of telescoped caseless ammunition inthe loaded position therein illustrating an annular cavity in the aftend of the chamber and the spacial relationships of the chamber cavityand the telescoped caseless round.

FIG. 2 is a longitudinal View partly in section of an embodiment of afree-volume chamber of this invention containing a round of telescopedcaseless ammunition in the loaded position, said chamber comprised of achamber housing and a chamber sleeve inserted into the housing, saidchamber sleeve having both forward and aft cavities.

FIG. 3 is an elevational view partly broken away and in section of thechamber sleeve and telescoped caseless round of FIG. 2 furtherillustrating the chamber sleeve design and the spacial relationship ofchamber sleeve cavities to the telescoped caseless round loaded therein.

In FIG. la free-volume chamber 10 and a barrel 12 are shown as anintegral assembly. The chamber 10 has a cavity 14 in the shape of anannular groove in its aft end about the inside surface 16 of chamber 10,said cavity 14 having a forward surface 18 and an aft surface 20. Atelescoped round of caseless ammunition 22 comprised of a projectile 24,propellant charge 26, and primer 28 is in the loaded position in chamber10, with the forward edges 30 of the propellant charge 26 in contactwith the forward surface 32 of the chamber 10. The projectile 24 issecured at the forward end of propellant charge 26 with a centering ring27 and is secured at the aft-end of the propellant charge 26 with apropellant plug 29. Projectile 24 has a rotating band 34 having aforward rim 36. The forward surface 18 of cavity 14 is no fartherforward than the forward rim 36 of rotating band 34. The longitudinaloutside surfaces 38 of propellant charge 26 and the inside surface 16 ofchamber 10 are contiguous over the length of propellant charge 26 withthe exception of that portion of propellant charge 26 which is oppositethe symmetrically distributed free-volume provided by cavity 14. Theinside surface 16 of chamber 10 provides support for the propellantcharge 26 contiguous therewith. The portion of the propellant charge 26opposite cavity 14 is not so supported.

In FIG. 2 a free-volume chamber is shown comprised of a chamber housing40 and a chamber sleeve 42 inserted into the chamber housing 40. Thechamber sleeve 42 has an overall outside configuration coinciding withthe inside surface 44 of the chamber housing 40 and has an outsidediameter slightly smaller than the inside diameter of the chamberhousing 40 to provide for ease of insertion of the chamber sleeve 42into the chamber housing 40. A telescoped round of caseless ammunition46 is shown loaded into the chamber sleeve 42. The chamber sleeve 42 hassymmetrically spaced aft cavities 48 and forward cavities 50 about itsinside surface 52 providing the free-volume for the chamber.

In FIG. 3, the telescoped caseless round 46 comprised of a propellantcharge 54, projectile 56 and primer 58 is further illustrated as loadedin chamber sleeve 42. The projectile 56 has a rotating band 60 having aforward rim 62 and a rearward rim 64. The aft cavities as represented bycavity 48 of the chamber sleeve 42 are spaced about the chamber sleeve42 so that the freevolurne provided by the cavities is symmetricallydistributed about the propellant charge opposite the cavities, andpositioned, in relation to the telescoped caseless round 46, aft of theforward rim 62 of rotating band 60. The forward edge 66 of cavity 48 andthe rearward rim 64 of rotating band 60 are in alignment. The forwardcavities are represented by cavity 50 are symmetrically spaced about theforward end of chamber sleeve 42. The forward cavities 50 are positionedforward of the forward rim 62 of rotating band 60 so that there issupport provided by the chamber sleeve 42 directly forward of therotating band 60. The propellant charge 54 is contiguous with the insidesurface 52 of chamber sleeve 42 except for those areas of the propellantcharge 54 opposite the forward cavities 50 and aft cavities 48, where nosupport for propellant charge 54 is provided.

ties. The spacial relationship of the cavities of the chamber sleeve andthe telescoped round of caseless ammunition is as illustrated in FIG. 3.The total free-volume provided by the chamber calculated as a percentageof the total volume of the propellant charge of the telescoped caselessrounds is about 35%.

Eight rounds of telescoped caseless ammunition are assembled having likeprimers, propellant charges, and 20 mm. projectiles and are fired in thefree-volume chamber described. Rounds 1-4 have the projectile manuallyseated in the gun barrel and the propellant charge loaded in the chamberprior to firing of the round to essentially eliminate gas loss past theprojectile. Rounds 5-8 are fired as telescoped caseless rounds. Resultsof the firings are contained in Table II.

TAB LE II Charge Chamber Chamber Round Weight, Velocity, pressurepressure N 0. (grains) (ft./sec.) (p.s.i.) (p.s.i.) Round characteristic732.1 3, 652 50, 300 62,000 Projectile seated. 732. 7 3, 674 50, 300 60,000 Do. 732. 6 3, 687 52, 500 64, 000 Do. 723. 6 3, 647 51, 000 62, 000Do. 724. 6 3, 683 64, 800 67, 000 Do. 729. 8 3, 638 51, 400 63, 000 Do.724. 1 3, 667 55, 500 68, 000 Do. 731. 5 3, 609 50, 300 61, 000 D0.

1 Measured over a 10-foot interval beginning 31 feet from the gunmuzzle. 2 Measured by copper crusher gauge. 3 Measured by transducer.

The following examples will further illustrate this invention. Example 1illustrates the loss of ballistic efiiciency when firing a telescopedround of caseless ammunition in a conventional (close fitting) chamber.

EXAMPLE 1 TABLE I.CASELESS ROUNDS FIRED FROM A CONVEN- TIONAL (CLOSEFITTING) CHAMBER Round Round character- Propellant Velocity, Cherub e rN0. isties weight, grains itJsec. pressure,p.s.1.

1 Projectile 716.7 2, 998 63,000

telescoped.

2 Projectile seated... 716. 7 3, 650 63, 000

The loss of ballistic efficiency of the telescoped caseless round(round 1) due probably to gas loss prior to seating of the projectile ofthe round is illustrated by the decreased velocity for that round.

The following example illustrates the improvement in ballisticperformance resulting from the firing of a telescoped round of caselessammunition in a free-volume chamber of this invention.

EXAMPLE 2 A free-volume chamber designed for receiving caselessammunition is prepared and is comprised of a chamber housing and chambersleeve having forward and aft cavi- As can be seen from Table II, themeasured velocity of the projectiles which are telescoped issubstantially the same as the measured velocity for like rounds in whichthe projectiles are seated prior to firing. The substantially equivalentballistic results from the firing of these rounds as compared to theballistic results of Example 1 illustrate the efiectiveness of thefree-volume chamber for increasing the ballistic efficiency oftelescoped caseless ammunition.

The free-volume chamber of this invention provides areas of support andnon-support about the periphery of the propellant charge of the round oftelescoped caseless ammunition loaded therein. It is necessary in orderthat proper support be provided for the propellant charge, that theoutside longitudinal configuration of the telescoped caseless round andthe inside overall longitudinal configuration of the chamber, i.e., theconfiguration excluding cavities, be essentially the same so that theportion of the propellant charge not opposite a cavity is contiguouswith the inside surface of the chamber.

The free-volume chamber of this invention can be prepared as a one pieceor integral chamber or it can be prepared as a two piece chamber in theform of a chamber housing having a chamber sleeve insertable therein.When the free-volume chamber is comprised of a chamber housing and achamber sleeve, the inside longitudinal configuration of the chamberbody and overall outside longitudinal configuration of the chambersleeve, i.e., the configuration excluding any cavities or voidscompletely through the sleeve, must be essentially the same. Thecavities in the free-volume chamber can be made in any desired shape.These cavities can, for example, consist of pockets, or annular groovesin the integral chamber, or they can consist of pockets, annular groovesor complete voids in the chamber sleeve of the two piece free-volumechamber. The spacing of the cavities can be either symmetrical ornon-symmetrical about the freevolume chamber. It is preferred, however,to space and size the cavities so that the free-volume provided issymmetrically distributed.

An essential feature of the free-volume chamber of this invention isthat the chamber have at least one aft cavity wherein the forward edgeof the aft cavity is located no farther forward in the chamber than theforward rim of the rotating band of the projectile. Other cavities canbe located forward of the forward rim of the rotating band of theprojectile. It is important, however, to provide some support around thearea of the propellant charge opposite and forward of the forward rim ofthe rotating band. The amount of support area to be provided by thechamber forward of the forward rim of the projectile rotating band willvary depending on the overall configuration of the telescoped round, thephysical strength of the molded propellant charge, and the size anddistribution of free volume provided by the aft cavities of the freevolume chamber. The purpose of the support area opposite and forward ofthe forward rim of the rotating band is to prevent breakup of theforward portion of the propellant charge until after the projectile hasstarted to move into the barrel of the gun.

As will be evident to those skilled in the art, various modificationscan be made or followed, in light of the foregoing disclosure anddiscussion, without departing from the spirit or scope of the disclosureor from the scope of the claims.

What I claim and desire to protect by Letters Patent is:

1. A free-volume chamber designed for receiving a round of telescopedcaseless ammunition, said free-volume chamber defined in relation to around of telescoped caseless ammunition comprising a propellant charge,a projectile having a rotating band, and a primer, said round placed ina loaded position in said free-volume chamber; said free-volume chambercomprising a chamher body having at least one aft cavity in its insideperipheral surface whereby an area of non-support is provided for thepropellant charge opposite said cavity, the forwardmost portion of saidaft cavity located no farther forward in the chamber body than theforward rim of the rotating band of the projectile, the remainingportion of the propellant charge being contiguous with the insidesurface of the chamber body which provides support for the propellantcharge contiguous therewith, whereby increased ballistic performanceresults upon firing the telescoped caseless round in the free-volumechamber.

2. The free-volume chamber of claim 1 having at least one forward cavityin its inside peripheral surface whereby an area of non-support isprovided for the portion of the propellant charge opposite said forwardcavity, said forward cavity located forward of the forward rim of theprojectile rotating band.

3. The free-volume chamber of claim 2 wherein the areas of non-supportprovided by the forward and aft cavities are symmetrically distributedabout the propellant charge.

4. A free-volume chamber designed for receiving a round of telescopedcaseless ammunition, said free-volume chamber defined in relation to around of telescoped caseless ammunition comprising a propellant charge,a projectile having a rotating band, and a primer, said round placed ina loaded position in said free-volume chamber; said free-volume chambercomprising a chamber body comprised of a chamber housing and a chambersleeve, said chamber sleeve being inserted into said chamber housing andhaving an outside longitudinal configuration corresponding to the insidelongitudinal configuration of the chamber housing and an inside overalllongitudinal configuration corresponding to the longitudinal outsideconfiguration of the telescoped round of caseless ammunition loadedtherein, said chamber sleeve having at least one aft cavity in itsinside peripheral surface whereby an area of non-support is provided forthe propellant charge opposite said cavity, the forwardmost portion ofsaid aft cavity being located no farther forward in the free-volumechamber than the forward rim of the rotating band of the projectile, theremaining portion of the chamber sleeve being contiguous with thepropellant charge of the round and providing support therefor, wherebyimproved ballistic performance results from firing of the telescopedcaseless round in the free-volume chamber.

5. The free-volume chamber of claim 4 having at least one forward cavityin the inside peripheral surface of the chamber sleeve whereby an areaof non-support is provided for the propellant charge opposite saidforward cavity, said forward cavity located forward of the forward rimof the projectile rotating band.

6. The free-volume chamber of claim 5 having at least two aft cavitiesand at least two forward cavities symmetrically distributed about thechamber sleeve, said freevolume chamber providing symmetricallydistributed areas of support and non-support about the propellantcharge.

References Cited UNITED STATES PATENTS 2,866,412 12/1958 Meyer et al.102-38 3,439,635 4/1969 Hensley 10238 BENJAMIN A. BORCHELT, PrimaryExaminer C. T. JORDAN, Assistant Examiner U.S. Cl. X.R. 10238 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. U.S.P,3,528,187 Dated Inventor(s) Joseph I. Harrell (Case 1) I It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

j Table II, Rounds 5 through 8, under Round Characteristic should read"Projectile Telescoped" SIGNED MD SEALED WI: 17m

(SEAL) A Emu-mix.

I mmr. an: '4 I: a.

Auesting Officer Gel-1:31am 01' Patent:

